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S2 binomial distribution help ?

Hello guys

so the problem is :

There are two types of notes: One with one strip and the other with two strips

Let X be prob of a note having two strips. Which is 0.3
In a sample of 8 NOTES:

X~B(8,0.3)

FIND the prob of MORE THAN THREE notes having ONE STRIP :

... Let Y be the prob of note having one strip

So from the question I assumed P(X>3) BUT how do I work out the inverse prob
I always have trouble working it out

I tried : P(Y>3)=P( X LESS OR EQUAL TO 2)

but it isn't right. The right ANSWER is P(X Less or Equal to 4 ) I was like WTF ?

DOES anyone know a method to get these inverse prob right ? arghhh thanks guys :biggrin: